Conventionally, in answer to needs for compactness and cost reduction of cameras, there is a desire to employ a single lens as a camera lens. However, with a construction based only on a single lens of an aspheric surface, there is little freedom for design parameters, and correction of spherical aberration and coma is possible at best; thus, correction of chromatic aberration and curvature of field is difficult.
Therefore, Patent Document 1 makes an attempt to correct chromatic aberration by adding a diffraction grating on the surface of a single lens.
A diffraction grating has inverse dispersion and anomalous dispersion, and has a large chromatic aberration correction ability. Therefore, using a diffraction grating makes it possible to correct the chromatic aberration which occurs on a single lens.    [Patent Document 1] Japanese National Phase PCT Laid-Open Publication No. 8-508116